Revert back from using reserved identifiers

Author: AlexeySachkov

sycl/include/sycl/accessor.hpp

@@ -1195,9 +1195,9 @@ class __SYCL_SPECIAL_CLASS __SYCL_TYPE(accessor) accessor :
   using reference = DataT &;
   using const_reference = const DataT &;
 
-  using iterator = typename detail::__accessor_iterator<DataT, Dimensions>;
+  using iterator = typename detail::accessor_iterator<DataT, Dimensions>;
   using const_iterator =
-      typename detail::__accessor_iterator<const DataT, Dimensions>;
+      typename detail::accessor_iterator<const DataT, Dimensions>;
   using difference_type =
       typename std::iterator_traits<iterator>::difference_type;
 
@@ -2099,28 +2099,28 @@ class __SYCL_SPECIAL_CLASS __SYCL_TYPE(accessor) accessor :
   bool operator!=(const accessor &Rhs) const { return !(*this == Rhs); }
 
   iterator begin() const noexcept {
-    return iterator::__get_begin(
+    return iterator::getBegin(
         get_pointer(),
         detail::convertToArrayOfN<Dimensions, 1>(getMemoryRange()), get_range(),
         get_offset());
   }
 
   iterator end() const noexcept {
-    return iterator::__get_end(
+    return iterator::getEnd(
         get_pointer(),
         detail::convertToArrayOfN<Dimensions, 1>(getMemoryRange()), get_range(),
         get_offset());
   }
 
   const_iterator cbegin() const noexcept {
-    return const_iterator::__get_begin(
+    return const_iterator::getBegin(
         get_pointer(),
         detail::convertToArrayOfN<Dimensions, 1>(getMemoryRange()), get_range(),
         get_offset());
   }
 
   const_iterator cend() const noexcept {
-    return const_iterator::__get_end(
+    return const_iterator::getEnd(
         get_pointer(),
         detail::convertToArrayOfN<Dimensions, 1>(getMemoryRange()), get_range(),
         get_offset());